Splattermaster

[Pete, WA2CWA]

That’s the problem! It's not people who run too much audio or don’t know or care about what they're doing; it’s the proliferation of SDR out there. Stomp out SDR radios and nobody will notice, well maybe. I started in Ham radio back when everything was already SSB and have to wonder what it must have been like back in the forties, fifties and sixties when everyone ran AM? Would think that splatter was everywhere along with heterodynes and the like. I kind of like to listen to 7.290 and have been amazed by the amounts of heterodynes form other stations on frequency at times. Have only heard this once or twice on 1.885 and I am just not proficient enough operator to work eighty so I avoid that band. But have to wonder if things were not a lot worse back in the old days? Maybe because the radios and things like SDR are so much better we notice this stuff more?

And many, back in the "good old days", had crappy receivers (compared to today's modern marvels) but we all survived on AM. Most AM off the shelf transmitters were tailored to 6 KHz bandwidth. It was always fun operating Field Day during the late 50's and early 60's on AM. Lots of beer, and after awhile, you didn't even notice the heterodynes.

[Pete, WA2CWA]

I have been following this thread and looking at the YouTube vids. And I wonder how we can analyze what is going on in the TX to make it so dam bad??Fred

Fred whoever posted this is using a PRO 1,2 or 3 with only  6 db attenuation.  They are so close to Robert that they probably could remove the antenna and still have gross overload. 

And, on several of those videos where the video camera panned the front panel of the 756 PRO II, it looks like the Noise Blanker is engaged (button light is on). The 756 PRO series are cool receivers but they're not high quality spectrum analyzers.

[flintstone mop]

That’s the problem! It's not people who run too much audio or don’t know or care about what they're doing; it’s the proliferation of SDR out there. Stomp out SDR radios and nobody will notice, well maybe. I started in Ham radio back when everything was already SSB and have to wonder what it must have been like back in the forties, fifties and sixties when everyone ran AM? Would think that splatter was everywhere along with heterodynes and the like. I kind of like to listen to 7.290 and have been amazed by the amounts of heterodynes form other stations on frequency at times. Have only heard this once or twice on 1.885 and I am just not proficient enough operator to work eighty so I avoid that band. But have to wonder if things were not a lot worse back in the old days? Maybe because the radios and things like SDR are so much better we notice this stuff more?

"Back in the day" all there seemed to be was table top transmitters and a desk KW, here and there. The well appointed station might have Collins RX/TX. There were folks who really knew electronics cuz they had to draw schematics of circuits asked in the FCC test.
The bands were full of hetrodynes. There was a good Ham friend of mine that was around when the change was taking place to SSB and he was so happy that AM was going by the wayside. I don't think that the CB mentality was rampant as it is now.

Fred

[K1JJ]

Let it be said that it's not an easy task to build or modify an old rig - or even get a commercial rig to be clean.  There are many adjustments involved and it doesn't take more than one incorrectly set to cause excessive splatter.  Even picking the wrong tube for the job or using incorrect parts is enough to make it a struggle.

For example, it took me about 10 years of experimenting with various homebrew and commercial linear amplifiers before I finally found a combination that was clean enough to run in the DX window without complaints.  There are nights when the noise level is S3 and the locals are S9+40 over.  If we even run a rig that has an acceptable 3rd IMD at -30db down, our SSB splatter may still be S9+10  3-4 kc up the band. Thus a rig that is not at least this clean will cause problems.

Now, on AM, we have normal bandwidth that is wider, like 4-6khz audio and more. (8-12khz total bandwidth)   This makes the problem of running a clean rig even more important since we co-exist with ssb stations that have their own ~3kc spacing standards.  

My hat's off to the guys on the band who figure out what it takes to run a clean QRO rig.  It doesn't matter if we are running SSB or AM through a linear, the IMD will be roughly the same. At times I've heard some exceptionally clean ssb rigs that were S9+50 over and they barely had side chatter 3.5kc away. I will sometimes break in and axe them what kind of amplifier they are running and compliment them on the cleanliness. Heck, I want to know how they pull it off.   A fast way to tell a clean amp is to listen on the opposite sideband. (both TX and RX on ssb) If we hear barely any audio, the amplifier is probably clean. If there are problems, the audio on the opposite side may be down only 20db. This assumes the exciter has good opp sideband suppression.

Jay/W1VD brought up a good point in another thread - if we reduce our power output by 3db, the IMD products improve by about 9db. This is tremendous!  The same applies to AM. If we stress our modulators and final by 3db less, (1/2 power) they may have the headroom and final amplifier capability and linearity to do better, in many cases.

Also, backing down the audio to -90% negative and  115% positive maximum with the audio rolled off to 4.5khz can do wonders if the rig is acting linearly in the first place.  

As Al/VTP said, the final check is to have a buddy analyze our rig on an SDR receiver and video tape it too.

Again, it's NOT an easy task to get an overall station system to be clean.  Being that many of us are not industry professionals, I'm surprised there are not more problems like this on the air.   It hurts all AMers when a few are having problems getting their rigs ironed out.  Let's help each other when we can and over time the situation will improve.

T

[W5COA]

Will try to keep this on topic, but to answer some questions raised, here goes:

- Yes, back in  the last century, specifically during the '50's and '60's, the bands were full of heterodynes. We just learned to live with them. As for splatter, someone would generally break in and tell you, and you would turn down the audio gain. It happened to me while running high level negative cycle loading, and I thanked whoever told me. I had no test equipment, and depended upon others to tell me if I was OK or not.

- I spent a good part of my career testing amplifiers for distortion: two tone intermod, linearity, group delay, etc. Every type of amplifier is a little different, but I came to the conclusion that if you wanted to operate in the linear region, you needed to back off at least 6dB from saturation, and preferably 10dB.

Translated to ham terms, if you have a linear amp capable of 1KW saturated output on CW, for clean AM linear service you need to run it at no more than 100W output. If you already have a 100W output plate modulated transmitter, a 1KW linear won't buy you a thing. You can push it to 250W output, but you will generate noticeable distortion products. In essence, you are trying to amplify three signals, the carrier and two sidebands.

I realize that this discussion does not apply to the plate modulated transmitter that is the subject of this thread, but  these items were brought up along the way.

73, Jim

[Opcom]

That’s the problem! It's not people who run too much audio or don’t know or care about what they're doing; it’s the proliferation of SDR out there. Stomp out SDR radios and nobody will notice, well maybe. I started in Ham radio back when everything was already SSB and have to wonder what it must have been like back in the forties, fifties and sixties when everyone ran AM? Would think that splatter was everywhere along with heterodynes and the like. I kind of like to listen to 7.290 and have been amazed by the amounts of heterodynes form other stations on frequency at times. Have only heard this once or twice on 1.885 and I am just not proficient enough operator to work eighty so I avoid that band. But have to wonder if things were not a lot worse back in the old days? Maybe because the radios and things like SDR are so much better we notice this stuff more?

"Back in the day" all there seemed to be was table top transmitters and a desk KW, here and there. The well appointed station might have Collins RX/TX. There were folks who really knew electronics cuz they had to draw schematics of circuits asked in the FCC test.
The bands were full of hetrodynes. There was a good Ham friend of mine that was around when the change was taking place to SSB and he was so happy that AM was going by the wayside. I don't think that the CB mentality was rampant as it is now.

Fred

No, the flavor was anti-CB, and CBers were considered "riff-raff". It was after the technical testing standards were dumbed down that the "CB" problem began.

[W2PFY]

That's the last thing we need. Seek out FeeCee intervention, and you just might get what you asked for, but not like what you get.

I think your right Don. I was thinking that the FCC would be there to help repair the problem and help the poor ham guy out? What was I smoking that night??

[w1vtp]

Tom & others

Comments well taken.  We are all engineers, by avocation.  We are supposed to be running stations using good engineering practice as per part 97.  I

Al

[KM1H]

I use a Bird 4273 sampler (rated at 5 KW) in conjunction with  a combination of Weinschel power attenuators directly connected to my Flex 1500 for precisely this type of test.  I then absolutely know what my splatter factor is.

Im using an old military directional coupler that has LC connectors so its obviously for a bit more than exciter power. Ive run 5KW thru it and into several high power attenuators for IMD testing into the SA.

I should just wind a big toroid!

Carl

[WD8BIL]

And I've never heard Carl splatter either.

[k4kyv]

We are all engineers, by avocation.  We are supposed to be running stations using good engineering practice as per part 97.

Very true, but unfortunately, those of us in the AM community who build, restore and convert our own transmitters are but a tiny minority of the Hammy Hambone community-at-large.  To-day, most hams set up their station by credit card, not by Handbooks and engineering texts. Hell, it is not unusual to see postings on the various amateur radio forums by Extra Class licensees, asking for instructions on how to put together a simple coax-fed half wave dipole, or else asking where they can buy one ready-made.

As far as I know, none of the major ham equipment manufacturers any longer produce a modulation monitoring scope capable of viewing envelope and trapezoid patterns.  The big ones, like Yaesu, Kenwood and even Heathkit used to offer monitor scopes custom made to go with their transceiver/leen-yar lines, but evidently quit producing them due to lack of customer demand.  It most likely reached a point that not many of their customers knew how to interpret scope readings, so why would they want to purchase one?.

I might add, a waterfall or pan-adaptor display on a transceiver is not the same thing as spectrum analysis using a precision measuring instrument. I believe such equipment is readily available at not too great a cost, in the form of a black box that attaches to the rf sampler and uses an external computer with accessible video card to produce the display.

[W2VW]

And I've never heard Carl splatter either.

You'd have to hear him to hear him splatter.

[K5IIA]

I think dr. Tron is taking appointments in the am window over the next few weeks if anyone needs a transmitter checkup.

[Pete, WA2CWA]

As far as I know, none of the major ham equipment manufacturers any longer produce a modulation monitoring scope capable of viewing envelope and trapezoid patterns.  The big ones, like Yaesu, Kenwood and even Heathkit used to offer monitor scopes custom made to go with their transceiver/leen-yar lines, but evidently quit producing them due to lack of customer demand.  It most likely reached a point that not many of their customers knew how to interpret scope readings, so why would they want to purchase one?.

It might also imply that their equipment might need one if it was an additional accessory.

Of course, if you don't read the instruction/operating manual first to understand the features, functions, and specifications of any particular new "high-tech" wizzy rig, the chance of screwing up something on transmit or receive is probably quite high.

[k4kyv]

It might also imply that their equipment might need one if it was an additional accessory.

 

EVERY rig needs one.  To make sure the signal is not flat-topping on positive peaks.  On AM, to make sure negative peak modulation doesn't exceed 100%. To show if anything unusual is occurring with the signal.

Weird distortion (like parasitics) may show up readily visible on the envelope pattern. I couldn't count the number of times I first discovered something wrong with my signal when I noticed that the scope pattern had taken a turn towards the abnormal.

Operating a phone rig without a monitor scope is like driving a car at night with the headlights turned off.

[Jim, W5JO]

It might also imply that their equipment might need one if it was an additional accessory.

 

EVERY rig needs one.  To make sure the signal is not flat-topping on positive peaks.  On AM, to make sure negative peak modulation doesn't exceed 100%. To show if anything unusual is occurring with the signal.

Weird distortion (like parasitics) may show up readily visible on the envelope pattern. I couldn't count the number of times I first discovered something wrong with my signal when I noticed that the scope pattern had taken a turn towards the abnormal.

Operating a phone rig without a monitor scope is like driving a car at night with the headlights turned off.

Don, sadly, a lot of people who operate AM with high power cannot interprete what they see on a scope.  I don't recall any questions about reading a scope on any of the tests.  I haven't looked in a long while but don't remember any.   About the only people I know that can read one accurately participate in AM or CW modes and build or repair their own equipment.  As you know there are people out there who work on equipment and don't have a scope.  Most of them are just parts changers.

There are other long time hams who have never seen a scope and wouldn't know how to read it either as I mentioned earlier, I know of a guy who works on equipment and says he uses a spectrum analyzer to set modulation percentage. 

[W2XR]

It might also imply that their equipment might need one if it was an additional accessory.

 

EVERY rig needs one.  To make sure the signal is not flat-topping on positive peaks.  On AM, to make sure negative peak modulation doesn't exceed 100%. To show if anything unusual is occurring with the signal.

Weird distortion (like parasitics) may show up readily visible on the envelope pattern. I couldn't count the number of times I first discovered something wrong with my signal when I noticed that the scope pattern had taken a turn towards the abnormal.

Operating a phone rig without a monitor scope is like driving a car at night with the headlights turned off.

Don, sadly, a lot of people who operate AM with high power cannot interprete what they see on a scope.  I don't recall any questions about reading a scope on any of the tests.  I haven't looked in a long while but don't remember any.   About the only people I know that can read one accurately participate in AM or CW modes and build or repair their own equipment.  As you know there are people out there who work on equipment and don't have a scope.  Most of them are just parts changers.

There are other long time hams who have never seen a scope and wouldn't know how to read it either as I mentioned earlier, I know of a guy who works on equipment and says he uses a spectrum analyzer to set modulation percentage. 

Jim,

A sad commentary indeed on the technical caliber and expertise of many radio amateurs nowadays.

73,

Bruce

[ke7trp]

I went to great lengths to make sure my Rig does not do that.  The comments about robert are just crazy.  In the end, its up to the operator to feed any transmitter, Roberts or a BC rig with the correct audio gear to filter it. If you run full audio you get wide audio through either type of rig.  In fact, Robert always told me to never go past 7KC period and the right gear is needed ahead of the rig.

The one thing I will point out as have others is the front end overload. That icom wont take this at ALL.  I have that icom sitting here.  If that man would put in some ATT and back it down, he would not hear the Am'r at all. If you hit that icom with any kind of big signal, Its splatter city.

C

[WD8BIL]

Should read;

"If you hit that icom with any kind of big signal, Its splatter IMD city. "

Sorry C, I'm in a picky mood today. Nothing personal!

[WA3VJB]

"If you hit that icom with any kind of big signal, Its splatter IMD city. "

Good point, Buddly. Using the word "splatter" invariably points at the transmitter, when it could be intermod at the receiver.

There is a tendency among people who complain to blame our "old gear" before fully exploring whether their "new" receiver could be vulnerable to problems, either by its design or by mis-adjustment.

There was a guy in NJ who used to beat up on us when there was an AM QSO around 3825Kc. This was before the FCC reapportioned the phone band, so a few years ago now.

He was convinced we were "splattering," and aimed most of his bile at me in particular.  I went through and checked things like neutralization, my grid drive, and other parameters where problems might not show up on the 'scope, because I knew I wasn't hitting baseline on modulation peaks.

No problems found.

It was then that I approached a well-known Dog X-Ray operator who has published a number of papers and has a website with equipment reviews.  I said I had received multiple complaints from one person, and asked whether he could explain to me the potential risk of receiver problems, if, for example, the noise blanker or pre-amp were selected when encountering a strong signal.  

I deliberately did NOT disclose what mode I was on.

I got a nice discussion of how, indeed, a receiver could be the problem, and he even named a few brands and models known to be particularly vulnerable.  He followed up by asking about my setup, and it was then that the entire tone of the conversation changed to one of presuming my "old gear" on AM was far more likely to blame than any modern transceiver.

I had gotten my answer (the first part), and left it there.

[WD8BIL]

The Yeasu 1000D was a monster for this until someone figured out the filter switching diodes needed to be PINs. Once changed over the receiver really perks up.
The 1000MP has similar problems and with so many in the field you're bound to excite one sooner or later.

[KM1H]

And I've never heard Carl splatter either.

Moving targets are hard to hit   However Ive had my share of reports especially when using a new rig and the monitors are on other benches/rigs. The best monitors are the guys complaining or those I ask to listen

With AM capability from 160 to 2M it gets hard to remember all the best settings.

[W2VW]

And I've never heard Carl splatter either.

With AM capability from 160 to 2M it gets hard to remember all the best settings.

On usually works.

[WQ9E]

The hams most motivated to be "kilocycle cops" are generally those least suited for the position.   Pseudo spectrum analyzers built into modern gear and adopted by the technologically challenged have not helped the situation.

[Pete, WA2CWA]

It might also imply that their equipment might need one if it was an additional accessory.

 

EVERY rig needs one.  To make sure the signal is not flat-topping on positive peaks.  On AM, to make sure negative peak modulation doesn't exceed 100%. To show if anything unusual is occurring with the signal.

Weird distortion (like parasitics) may show up readily visible on the envelope pattern. I couldn't count the number of times I first discovered something wrong with my signal when I noticed that the scope pattern had taken a turn towards the abnormal.

Operating a phone rig without a monitor scope is like driving a car at night with the headlights turned off.

I agree, but that wasn't the point. I was merely responding to your statement, "none of the major ham equipment manufacturers any longer produce a modulation monitoring scope capable of viewing envelope and trapezoid patterns". I also suspect that AM isn't high on the list of operational concerns for the major equipment manufacturers. And, even it there was, the challenges of interpreting the transmitted waveforms may not be within every ham's grasp. For those that can grasp the value of a monitor scope, a trip to a flea market and for $5 or so, one can generally acquire a scope suitable for transmitter output monitoring.